Gyrus Rectus Herniation Following Transsphenoidal Pituitary Adenoma Surgery: A Rare Case Report

Abstract

Background

The gyrus rectus (GR) is located at the base of the anterior cranial fossa, above the prechiasmatic optic nerves and optic chiasm. Herniation of the GR has been reported secondary to idiopathic causes or space-occupying lesions of the frontal lobe. However, GR herniation following transsphenoidal pituitary surgery has not been described previously.

Case Description

A 51-year-old woman with no comorbidities other than diabetes presented with visual disturbance in the right eye. Imaging revealed a non-functioning pituitary macroadenoma compressing the optic chiasm from below. The patient underwent microscopic transsphenoidal resection of the pituitary adenoma, achieving total removal. Early postoperative recovery was uneventful. Six-month follow-up MRI demonstrated inferior herniation of the GR into the sellar cavity, compressing the optic nerves superiorly. Visual complaints partially improved without further progression.

Conclusion

This case represents the first reported instance of GR herniation following transsphenoidal pituitary surgery. Awareness of this rare complication is essential when evaluating persistent or new-onset visual symptoms postoperatively.

Introduction

Although gyrus rectus (GR) herniation has been previously reported in idiopathic or tumor-related cases, its postoperative occurrence following pituitary surgery has not been documented. The GR is located at the base of the anterior cranial fossa, superior to the prechiasmatic optic nerves and the optic chiasm. ¹ Inferior herniation of the GR may compress the optic nerve or shift posteriorly toward the suprasellar cistern, producing chiasmal compression. ² Such displacement may result from space-occupying lesions of the frontal lobe (hemorrhage, tumor) and is associated with ipsilateral optic atrophy, visual loss, and papilledema. ³ Pituitary adenomas, craniopharyngiomas, aneurysms, astrocytomas, and meningiomas are the most common lesions of the sellar region. ^{4 5} The optic chiasm, where optic nerves intersect, is crucial for vision, and compression by the GR can mimic these lesions, leading to misdiagnosis or unnecessary interventions.

Anatomy and Pathophysiology

The GR is located on the medial surface of the frontal lobe, just above the lamina terminalis. Normally, it forms part of the basal frontal lobe within the anterior cranial fossa. In certain conditions, such as medial frontal lobe atrophy, intracranial pressure variations, or congenital variants, the GR may descend inferiorly over the optic chiasm, causing mechanical compression and progressive optic neuropathy. This displacement can be visualized on CT or magnetic resonance imaging (MRI) without any associated mass lesion.

Radiological Findings

MRI is the most effective tool for diagnosing GR herniation.

• Sagittal T1/T2-weighted sequences demonstrate the GR prolapsing over the chiasm.

• Coronal sections clarify the relationship between the optic chiasm and the herniated GR.

• The absence of a mass lesion is the key diagnostic feature.

Case Report

A 51-year-old woman with diabetes and no other comorbidities presented with visual impairment in the right eye. Preoperative visual field testing revealed bilateral superior scotomas. Fundus examination showed normal optic discs without papilledema. Hormonal evaluation was within normal limits, consistent with a non-functioning pituitary macroadenoma ( Fig. 1 ). The patient underwent microscopic transsphenoidal resection, achieving total tumor removal. No intraoperative cerebrospinal fluid (CSF) leak was observed. No early postoperative complications occurred, and she was discharged on postoperative day 3. At the 6-month follow-up, visual symptoms had improved but persisted. Visual field testing showed no progression. Neurological examination was normal. Follow-up MRI demonstrated inferior herniation of the GR into the sellar cavity, forming a V-shaped indentation on the optic nerves due to GR compression ( Figs. 2 and 3 ). Given the stable clinical status, observation was recommended.

Fig. 1.

Preoperative contrast-enhanced T1-weighted sagittal and coronal images demonstrating a pituitary macroadenoma with suprasellar extension causing compression of the optic chiasm (white arrows).

Fig. 2.

Postoperative MRI showing total excision of the adenoma and herniation of the gyrus rectus into the sellar cavity, indicated by the white arrows. MRI, magnetic resonance imaging.

Fig. 3.

T1-weighted sagittal and T2-weighted coronal images revealing herniation of the gyrus rectus into the sellar cavity, causing indentation of the optic nerve (white arrows).

Discussion

Optic nerve and chiasmal compression secondary to idiopathic or mass-related GR herniation has been reported, although its true incidence remains unknown. ^{1 3} To our knowledge, GR herniation following transsphenoidal pituitary surgery has not been previously reported. In our case, the preoperative macroadenoma compressed the optic chiasm and nerves inferiorly, causing visual field deficits. Postoperatively, imaging confirmed tumor removal, and the patient's visual complaints partially improved. Although optic nerve compression and visual loss secondary to idiopathic or tumor-induced GR herniation have been described, this case represents the first instance following transsphenoidal surgery.

GR herniation has previously been reported following medical treatment of functional pituitary adenomas, likely related to rapid tumor shrinkage and subsequent loss of intrasellar support. A similar mechanism may be responsible in the present case. No intraoperative CSF leak was observed; however, complete tumor resection and preoperative suprasellar extension may have contributed to postoperative empty sella formation and loss of diaphragma sellae support, predisposing to GR herniation. In the event of progressive herniation with visual deterioration, surgical re-exploration and sellar reconstruction to restore intrasellar support could be considered.

Conclusion

GR herniation should be considered in patients with persistent or new-onset visual symptoms following sellar or parasellar surgery. Awareness of this rare postoperative complication is essential for accurate diagnosis and management.